1. Field of the Invention
The present invention relates to a data processing apparatus and a data processing method and, more particularly, to a data processing apparatus and a data processing method that are configured to easily prevent apparatuses from getting in an abnormal state in which these apparatuses operate in an abnormal manner.
2. Description of the Related Art
For example, in a broadcasting station of satellite digital broadcasting, an image (a moving image) and so on are encoded by a predetermined encoding scheme, such as MPEG (Moving Picture Experts Group) or the like, and processing for error correction, such as convolution coding or the like, is executed on a resultant stream TS (Transport Stream). Further, in the broadcasting station, modulation processing, such as digital modulation or the like, is executed and a resultant modulated signal is transmitted as a broadcast signal.
The broadcast signal of satellite digital broadcasting that is transmitted as described above is received by receiving apparatuses, such as a digital TV (Television) and mobile phone. In each receiving apparatus, the received broadcast signal is demodulated and error correction processing is executed on the demodulated signal. Further, in each receiving apparatus, MPEG data (the data encoded by the MPEG scheme) arranged in packets (TS packets) constituting a stream obtained as a result of the error correction processing is decoded and images (and audio) obtained as a result of the decoding are reproduced.
As described above, in the receiving apparatus, an error caused during the transmission of each broadcast signal is corrected by executing error correction processing.
Meanwhile, in poor signal receiving environments, such as an environment in which the power of a broadcast signal to be received by the receiving apparatus is weak and an environment in which the noise included in a broadcast signal is large, for example, an error that cannot be corrected may occur or the demodulation of a broadcast signal may fail.
If an uncorrectable error occurs or the demodulation of a broadcast signal fails, a stream after error correction processing may become short or elongated. If such a stream (or packets constituting the stream) is given to a decoder for decoding MPEG data, the decoder and eventually the receiving apparatus may put in an abnormal state (for example, a hung-up state or a system runaway state) in which the receiving apparatus operates abnormally.
It is important in view of fail safe to prevent the receiving apparatus from getting in an abnormal state. One of prevention methods is the monitoring of PTS (Presentation Time Stamp), for example (refer to, for example, Japanese Patent Laid-Open Nos. 2006-157729 and 2007-012187, hereinafter referred to as Patent Documents 1 and 2).
To be more specific, in MPEG2, if the PTS included in a TS packet is damaged in terms of standard, the processing of the decoder is affected. Therefore, Patent Documents 1 and 2 disclose methods in which, PTS monitoring is executed and, if an abnormal PTS is detected, the corresponding TS packet is prevented from being outputted to the decoder and the abnormal PTS is corrected, thereby preventing the receiving apparatus from getting in an abnormal state.